Patient temperature control catheter with outer sleeve cooled by inner sleeve

ABSTRACT

A catheter has an inner sleeve through which refrigerant circulates to and from a source of refrigerant. The catheter also has an outer sleeve surrounding the inner sleeve, including a distal end thereof. The outer sleeve is filled with a frozen biocompatible substance. The refrigerant is separated from the biocompatible substance by one or more walls of the inner sleeve such that the refrigerant is isolated from a patient in whom the catheter is positioned by both the inner sleeve and the frozen biocompatible substance. The refrigerant circulates through the catheter when the catheter is positioned in the patient to maintain the biocompatible substance frozen as heat is transferred from the patient to the biocompatible substance.

FIELD OF THE INVENTION

The present application relates generally to patient temperature controlsystems.

BACKGROUND OF THE INVENTION

It has been discovered that the medical outcome for a patient sufferingfrom severe brain trauma or from ischemia caused by stroke or heartattack or cardiac arrest is improved if the patient is cooled belownormal body temperature (37° C.). Furthermore, it is also accepted thatfor such patients, it is important to prevent hyperthermia (fever) evenif it is decided not to induce hypothermia. Moreover, in certainapplications such as post-CABG surgery, it might be desirable to rewarma hypothermic patient.

As recognized by the present application, the above-mentioned advantagesin regulating temperature can be realized by cooling or heating thepatients entire body using a closed loop heat exchange catheter placedin the patient's venous system and circulating a working fluid such assaline through the catheter, heating or cooling the working fluid asappropriate in an external heat exchanger that is connected to thecatheter. The following U.S. patents, all of which are incorporatedherein by reference, disclose various intravascularcatheters/systems/methods for such purposes: U.S. Pat. No. 6,881,551 andU.S. Pat. No. 6,585,692 (tri-lobe catheter), U.S. Pat. No. 6,551,349 andU.S. Pat. No. 6,554,797 (metal catheter with bellows), U.S. Pat. No.6,749,625 and U.S. Pat. No. 6,796,995 (catheters with non-straight,non-helical heat exchange elements), U.S. Pat. No. 6,126,684, U.S. Pat.No. 6,299,599, U.S. Pat. No. 6,368,304, and U.S. Pat. No. 6,338,727(catheters with multiple heat exchange balloons), U.S. Pat. No.6,146,411, U.S. Pat. No. 6,019,783, U.S. Pat. No. 6,581,403, U.S. Pat.No. 7,287,398, and U.S. Pat. No. 5,837,003 (heat exchange systems forcatheter), U.S. Pat. No. 7,857,781 (various heat exchange catheters).

SUMMARY OF THE INVENTION

Accordingly, a catheter includes an inner sleeve through whichrefrigerant, which may be supercritical, circulates to and from a sourceof refrigerant and an outer sleeve surrounding the inner sleeve. Thecatheter has both a proximal end and distal end relative to the sourceof the refrigerant. The outer sleeve is filled with a biocompatiblesubstance, which may be frozen in non-limiting embodiments.Additionally, the refrigerant is separated from the biocompatiblesubstance by one or more walls of the inner sleeve such that therefrigerant is isolated from a patient in whom the catheter ispositioned by both the inner sleeve and the frozen biocompatiblesubstance. Refrigerant may thus circulate through the catheter when thecatheter is positioned in the patient to maintain the biocompatiblesubstance at a designated temperature (e.g., below the freezingtemperature/freezing point of the biocompatible substance) as heat istransferred from the patient to the biocompatible substance. Therefrigerant may be simply vented to ambient surroundings after coolingthe biocompatible substance, or recovered in a storage tank, orrecirculated in a closed loop through, e.g., a compressor.

If desired, the refrigerant may be Freon, and the biocompatiblesubstance may be saline or purified water. In non-limiting embodiments,the inner sleeve may be cylindrical. Furthermore, if desired, the outersleeve may also be generally cylindrical, except at proximal and distalends of the catheter. Further still, the inner sleeve and outer sleeveof the catheter may be coaxial with each other. Also in somenon-limiting embodiments, the inner sleeve may have an openingjuxtaposed with a proximal end of the inner sleeve and a closed distalend opposite the proximal end such that refrigerant may enter the innersleeve only through the proximal end and not pass through the distalend.

In other embodiments the refrigerant is supercritical gas such as CO2 inliquid phase, or liquid Nitrogen, or liquid Helium or other noble gases.For CO2 8 liters may be used for two hours. A temperature sensor oroptical sensor may be in communication with the biocompatible substanceto signal when it is at a temperature or state requiring additionalcooling. The biocompatible substance may be absent from the outer sleeveupon insertion into the patient so that the device essentially is in adeflated state during insertion, with the biocompatible substance beinginfused into the outer sleeve after the catheter has been inserted intothe patient. A pressure sensor/regulator may be provided for therefrigerant.

If desired, in addition to the above, the catheter may also have atleast one refrigerant sensor between the inner sleeve and outer sleeve.The refrigerant sensor may communicate with a control system engagedwith the catheter and, responsive to detecting refrigerant between thesleeves, generate a signal to the control system to cause the controlsystem to activate an audible and/or visual alarm if the temperature ofthe refrigerant deviates outside a designated temperature range.

In another aspect, a method for cooling a patient in whom a catheter isdisposed includes disposing a biocompatible fluid in the catheter. Themethod also includes removing heat from the biocompatible fluid usingrefrigerant circulating through the catheter. Additionally, the methodincludes shielding the patient from exposure to the refrigerant at leastin part using the biocompatible fluid.

In still another aspect, a system includes a catheter for cooling apatient in whom the catheter is disposed. The system also includes asource of refrigerant in fluid communication with the catheter. Thecatheter has an inner sleeve through which refrigerant circulates to andfrom the source of refrigerant. Additionally, the catheter has an outersleeve surrounding the inner sleeve that includes a distal end and isfilled with a biocompatible substance. The refrigerant circulatesthrough the catheter when the catheter is positioned in the patient tomaintain the biocompatible substance within a designated temperaturerange as heat is transferred from the patient to the biocompatiblesubstance.

The details of the present invention, both as to its structure andoperation, can best be understood in reference to the accompanyingdrawings, in which like reference numerals refer to like parts, and inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an example catheter engaged withan example heat exchange system;

FIG. 2 is a schematic diagram of a catheter having an inner sleeve andan outer sleeve in accordance with present principles;

FIG. 3 is a side cross-sectional view of a catheter in accordance withpresent principles, it being understood that the cross-sectionsrepresent refrigerant and biocompatible fluid, which may be frozen;

FIG. 4 is a transverse cross-sectional view of a catheter in accordancewith present principles;

FIG. 5 is a flow chart of non-limiting logic in accordance with presentprinciples; and

FIGS. 6-10 illustrate further details.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, an intravascular temperature managementcatheter 10 is in fluid communication with a catheter temperaturecontrol system 12 that includes a processor executing logic inaccordance with present principles, and as described in one or more ofthe patents referenced herein, to control the temperature of workingfluid circulating through the catheter 10 in accordance with a treatmentparadigm responsive to patient core temperature feedback signals. Inaccordance with present principles, the catheter 10 can be used toinduce therapeutic hypothermia in a patient 14 using the catheter, inwhich coolant such as but not limited to saline circulates in a closedloop, such that no coolant enters the body. Such treatment may beindicated for stroke, cardiac arrest (post-resuscitation), acutemyocardial infarction, spinal injury, and traumatic brain injury. Thecatheter 10 can also be used to warm a patient, e.g., after bypasssurgery or burn treatment, and to combat hyperthermia in, e.g., patientsuffering from sub-arachnoid hemorrhage or intracerebral hemorrhage.

As shown, working fluid such a refrigerant may be circulated between theheat exchange system 12 and catheter 10 through supply and return lines16, 18 that connect to the proximal end of the catheter 10 as shown.Note that as used herein, “proximal” and “distal” in reference to thecatheter are relative to the system 12. A patient temperature signalfrom a catheter-borne temperature sensor may be provided to the system12 through an electrical line 20 or wirelessly if desired.Alternatively, a patient temperature signal may be provided to thesystem 12 from a separate esophageal probe or rectal probe or tympanicsensor or bladder probe or other temperature probe that measures thetemperature of the patient 14.

The catheter 10, in addition to interior supply and return lumensthrough which the working fluid is circulated, may also have one or moreinfusion lumens connectable to an IV component 22 such as a syringe orIV bag for infusing medicaments into the patient, or an instrument suchas an oxygen or pressure monitor for monitoring patient parameters, etc.

The catheter 10 can be positioned typically in the vasculature of thepatient 14 and more preferably in the venous system of the patient 14such as in the inferior vena cava through a groin insertion point or thesuperior vena cava through a neck (jugular or subclavian) insertionpoint.

Now referring to FIG. 2, a schematic diagram of a catheter having aninner sleeve and an outer sleeve is shown. An intravascular temperaturemanagement catheter 24 has an inner sleeve 26 through which refrigerantmay circulate to and from a source of refrigerant, such as a cathetertemperature control system 36 engaged with the catheter as shown in FIG.2. The refrigerant may be, without limitation, Freon. The catheter alsohas an outer sleeve 28 substantially surrounding the inner sleeve 26.The outer sleeve 28 includes a distal end 32 and may filled with abiocompatible substance such as, but not limited to, saline.Furthermore, the biocompatible substance may be frozen, if desired. Inlieu of saline, in some non-limiting embodiments, the biocompatiblesubstance may be purified water or another substance having a freezingpoint temperature higher than the freezing point temperature of bloodin, e.g., a vein of a patient 34 in which the catheter 24 is disposed.

It may be appreciated from FIG. 2 that the refrigerant may be separatedfrom the biocompatible substance by one or more walls of the innersleeve 26 such that the refrigerant is isolated from the patient 34 inwhom the catheter is to be positioned by both the inner sleeve 26 andthe frozen biocompatible substance in the outer sleeve 28. Thus, therefrigerant circulates within the inner sleeve 26 of the catheter 24 totransfer heat through the inner sleeve 26 and away from thebiocompatible substance when the catheter 24 is positioned in thepatient 34 to maintain the biocompatible substance frozen as heat istransferred from the patient 34 to the biocompatible substance. It is tobe understood that the catheter 24 can be positioned typically in thevasculature of the patient 34 and more preferably in the venous systemof the patient 34 such as in the inferior vena cava through a groininsertion point or the superior vena cava through a neck (jugular orsubclavian) insertion point to transfer heat away from the patient 34.

Still in reference to FIG. 2, the catheter temperature control system 36(alternatively referenced herein as a heat exchange system) includes aprocessor executing logic described in one or more of the patentsreferenced herein. Thus, the control system 36 may control thetemperature of the refrigerant circulating through the inner sleeve 26in accordance with a treatment paradigm responsive to patient coretemperature feedback signals as described in further detail below. Inaccordance with present principles, the catheter 24 can be used toinduce therapeutic hypothermia in the patient.

Thus, as also shown in FIG. 2, working fluid may be circulated betweenthe control system 36 and catheter 24 through supply and return lines 38and 40. It is to be understood that the inner sleeve 26 has anopening(s) juxtaposed with the proximal end of the inner sleeve 26 and aclosed distal end opposite the proximal end such that refrigerant mayenter the inner sleeve 26 only through the proximal end and cannot passthrough the distal end. Note that as used herein, “proximal” and“distal” in reference to the catheter are relative to the control system36. Thus, the supply and return lines 38 and 40 connect a refrigerantbath 30 on the control system 36 that contains refrigerant to theopening(s) of the proximal end of the catheter 24 as shown such that acompressor 50 may compress (and help circulate) the refrigerant betweenthe bath 30 and inner portion of the catheter 24 defined by the innersleeve 26. If desired, an additional refrigerant pump may be providedout the outlet of the compressor to pump the refrigerant in the closedloop that includes the catheter, to remove heat from the biocompatiblesubstance.

As shown in FIG. 2, refrigerant sensor 42 may also be included on thecatheter 24 between the inner sleeve 26 and outer sleeve 28 to generatea refrigerant detection signal to the control system 36 through anelectrical line (not shown), or wirelessly if desired, responsive todetecting refrigerant between the sleeves. Further, in non-limitingembodiments, refrigerant detection signals may be sent at a non-limitingtemporal interval, when demanded, when the control system 36 is firstpowered on, etc. If the signal generated by the sensor 42 indicates thatrefrigerant is present in the chamber which is supposed to hold onlybiocompatible fluid, the control system 36 may activate an audibleand/or visual alarm 44. In an example embodiment, the sensor 42 is aFreon sensor.

Additionally, it is to be understood that while the biocompatiblesubstance may preferably be frozen while the catheter is positioned inthe patient 34, in other non-limiting embodiments the biocompatiblesubstance may optionally be a liquid substance or gaseous substance.Thus, while the outer sleeve 28 of the catheter 24 may be filled withthe biocompatible substance and subsequently closed such that nobiocompatible substance escapes from the outer sleeve 28 prior topositioning the catheter in the patient 34 (regardless of the currentstate of the biocompatible substance or whether the biocompatiblesubstance changes states), the biocompatible substance my instead becirculated to transfer heat away from the patient 34. Therefore, inalternative non-limiting embodiments, the biocompatible substance (whenin a fluid or gaseous form) may circulate between a biocompatiblesubstance bath 52 on the control system 36 and the catheter 24 throughoptional supply and return lines 46 and 48. The supply and return lines46 and 48 may connect to a proximal end portion of the catheter 24bearing the biocompatible substance as also shown in the non-limitingembodiment of FIG. 2. Additionally, in such an embodiment a substancepump (not shown) may circulate the biocompatible substance between thebath 52 and outer portion of the catheter 24 defined by the inner sleeve26 and outer sleeve 28.

It may now be appreciated that the biocompatible substance (when aliquid or gas) may also circulate in a closed loop such thatbiocompatible substance enters the body. It is to be understood that anydischarge of the biocompatible substance when frozen similarly does notenter the body. Lastly, the catheter 24, in addition to interior supplyand return lumens through which the refrigerant is circulated, may alsohave one or more infusion lumens 54 connectable to an IV component 56such as a syringe or IV bag for infusing medicaments into the patient,or an instrument such as an oxygen or pressure monitor for monitoringpatient parameters, etc.

Now in reference to FIG. 3, a side cross-sectional view of the catheter24 is shown. The catheter 24 still has the inner sleeve 26, the outersleeve 28, and the distal end generally designated 32. As may be seen inFIG. 3, the inner sleeve 26 and outer sleeve 28 may be coaxial with eachother. FIG. 3 also shows the sensor 42 as described above. Further, thecross-sectional view of FIG. 3 shows refrigerant 58 contained within theinner sleeve 26 and understood to be circulating to and from the controlsystem 36 (not shown in FIG. 3) through refrigerant supply and returnlines 38 and 40.

FIG. 3 also shows biocompatible substance 60 contained in the portion ofthe catheter 24 between the inner sleeve 26 and outer sleeve 28. It maybe appreciated from FIG. 3 that, in non-limiting embodiments, closedends 62 enclose the portion of the catheter 24 between the inner sleeve26 and outer sleeve 28 containing the biocompatible substance 60. It maytherefore be further appreciated that no biocompatible substance 60 mayescape from between the inner sleeve 26 and outer sleeve 28.

Moving on to FIG. 4, a transverse cross-sectional view of the catheter24 described in reference to FIG. 2 is shown. The catheter 24 still hasthe inner sleeve 26 and outer sleeve 28. FIG. 4 also shows therefrigerant 58 and biocompatible substance 60 referenced above. It maybe appreciated from the cross-sectional view of FIG. 4 that, innon-limiting embodiments, the inner sleeve 26 may be generallycylindrical.

Now in reference to FIG. 5, a flow chart of non-limiting logic inaccordance with present principles is shown. Beginning at block 64, abiocompatible substance in accordance with present principles isdisposed between an inner sleeve and an outer sleeve of a catheter inaccordance with present principles. At block 66, the space containingthe biocompatible substance is enclosed such that no biocompatiblesubstance may escape from the space in which it is disposed, except, insome embodiments, through the proximal end only. Moving to block 68, thebiocompatible substance in the catheter is frozen by, e.g., conductingan initial circulation of the refrigerant through the catheter, althoughin some embodiments this step is omitted to ensure the catheter retainssufficient flexibility for placement in the patient's vasculature. Thenat block 70, the catheter with the biocompatible substance ispositioned/placed into a patient. Concluding at block 72, a refrigerantis circulated in the inner sleeve to remove heat from the biocompatiblesubstance on the opposite side of the inner sleeve.

Note that in addition to the refrigerant sensor, a sensor 100 (FIG. 3)such as a temperature sensor or optical sensor may be disposed in thechamber holding the biocompatible substance to generate a signalrepresenting the temperature or state (i.e., frozen or liquid) thereof.If the biocompatible substance remains frozen the temperature should beat the freezing point of the biocompatible substance. A secondtemperature signal can be patient temperature as measured by anotherprobe or a temperature sensor external to the catheter.

Thus the biocompatible substance chamber is filled and the catheteradvanced into patient, circulating refrigerant to freeze thebiocompatible substance until patient target temperature as sensed bythe external sensor is reached. The internal temperature signal from thetemperature sensor inside the chamber holding the biocompatiblesubstance is monitored and if the temperature rises above the freezingpoint of the biocompatible substance prior to reaching patient targettemperature, refrigerant is circulated in catheter to freeze thebiocompatible substance. Once patient temperature reached, refrigerantis circulated only as needed to prevent a temperature rise in thebiocompatible substance, or the catheter may be removed from the patientaltogether.

While the particular PATIENT TEMPERATURE CONTROL CATHETER WITH OUTERSLEEVE COOLED BY INNER SLEEVE is herein shown and described in detail,it is to be understood that the subject matter which is encompassed bythe present invention is limited only by the claims.

What is claimed is:
 1. A catheter, comprising: an inner sleeve throughwhich refrigerant circulates to and from a source of refrigerant; and anouter sleeve surrounding the inner sleeve including a distal end thereofand filled with a frozen biocompatible substance, the refrigerant beingseparated from the biocompatible substance by one or more walls of theinner sleeve such that the refrigerant is isolated from a patient inwhom the catheter is positioned by both the inner sleeve and the frozenbiocompatible substance, the refrigerant circulating through thecatheter when the catheter is positioned in the patient to maintain thebiocompatible substance frozen as heat is transferred from the patientto the biocompatible substance.
 2. The catheter of claim 1, wherein therefrigerant is freon.
 3. The catheter of claim 1, wherein the frozenbiocompatible substance is saline.
 4. The catheter of claim 1, whereinthe inner sleeve is cylindrical.
 5. The catheter of claim 1, wherein theinner sleeve has an opening juxtaposed with a proximal end of the innersleeve and a closed distal end opposite the proximal end such thatrefrigerant may enter the inner sleeve only through the proximal end andcannot pass through the distal end.
 6. The catheter of claim 1, whereinthe sleeves are coaxial with each other.
 7. The catheter of claim 1,comprising at least one refrigerant sensor between the sleeves, therefrigerant sensor communicating with a control system engaged with thecatheter and responsive to detecting refrigerant between the sleeves,generating a signal to the control system for causing the control systemto activate an audible and/or visual alarm.
 8. A method for cooling apatient in whom a catheter is disposed, comprising: disposing abiocompatible fluid in the catheter; removing heat from thebiocompatible fluid using refrigerant circulating through the catheter;and shielding the patient from exposure to the refrigerant at least inpart using the biocompatible fluid.
 9. The method of claim 8, whereinthe refrigerant is Freon.
 10. The method of claim 8, wherein thebiocompatible fluid is saline.
 11. The method of claim 8, wherein thebiocompatible fluid is frozen.
 12. The method of claim 11, wherein therefrigerant circulating through the catheter maintains the biocompatiblesubstance frozen as the patient is cooled.
 13. The method of claim 8,wherein the catheter has an inner sleeve through which the refrigerantcirculates to and from a source of refrigerant and an outer sleevesurrounding the inner sleeve including a distal end thereof that isfilled with the biocompatible fluid.
 14. The method of claim 13, whereinthe inner sleeve has an opening juxtaposed with a proximal end of theinner sleeve and a closed distal end opposite the proximal end such thatrefrigerant may enter the inner sleeve only through the proximal end andcannot pass through the distal end.
 15. The method of claim 13, whereinthe sleeves are coaxial with each other.
 16. The method of claim 13,wherein the catheter includes at least one refrigerant sensor betweenthe sleeves, the refrigerant sensor communicating with a control systemengaged with the catheter and responsive to detecting refrigerantbetween the sleeves, generating a signal to the control system forcausing the control system to activate an audible and/or visual alarmwhen the temperature of the refrigerant deviates from a designatedtemperature range.
 17. A system, comprising: a catheter for cooling apatient in whom the catheter is disposed; and a source of refrigerant influid communication with the catheter; wherein the catheter has an innersleeve through which refrigerant circulates to and from the source ofrefrigerant; wherein the catheter has an outer sleeve surrounding theinner sleeve including a distal end thereof and filled with abiocompatible substance; and wherein the refrigerant circulates throughthe catheter when the catheter is positioned in the patient to maintainthe biocompatible substance within a designated temperature range asheat is transferred from the patient to the biocompatible substance. 18.The system of claim 17, wherein the biocompatible substance is frozen.19. The system of claim 17, wherein the inner sleeve of the catheter hasan opening juxtaposed with a proximal end of the inner sleeve and thedistal end opposite the proximal end such that refrigerant may enter theinner sleeve only through the proximal end and cannot pass through thedistal end.
 20. The system of claim 17, further comprising at least onerefrigerant sensor between the sleeves of the catheter, the refrigerantsensor communicating with a control system engaged with the catheter andresponsive to detecting refrigerant between the sleeves, generating asignal to the control system for causing the control system to activatean audible and/or visual alarm.